Oil-resistant thermoplastic and method of making



Patented Aug. 14, 1945 OIL-RESISTANT THERMOPLASTIC AND METHOD OF MAKING David J. Beaver, St. Albans, W. Va., assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Application November 1, 1941,

Serial No. 417,577

17 Claims.

This invention relates to new plastic products derived fromscrap or reclaimed rubbers and to the preparation of the same.

In accordance with this invention scrap or reclaimed rubber is treated with tolyl dichlor phosphine and retene in such proportion as to produce a vulcanizable plastic material which is resistant to the deteriorating effects of ozone, oxygen, oil, grease, gasoline afid other materials which exert a solvent action on rubber, and which at the same time possess a maximum of rubbery properties.

While the properties of the final products will in part be determined by the particular reclaimed or scrap rubber used as the starting material, the similarities are more striking than the differences. Inevery case it has been found that the solvent and ozone resistance of the original rubber' material are very greatly enhanced by reacting with technical tolyl dichlor phosphine and technical retene or retene oil in the proportions hereinafter set forth. Examples of scrap and reclaimed rubbers which have been successfully reacted include Midwest whole tire reclaim, Xylos ground scrap, Apex tube reclaim, Midwest ground black inner tube and ground truck peels. The above list is merely illustrative and it is to be understood that other scrap and reclaimed rubbers whether obtained by an acid or alkali reclaiming process can be reacted in similar manner.

The tolyl dichlor phosphine used in the present invention is the product resulting from the reaction of toluene and PC13 in the presence of anhydrous aluminum chloride and contains most if not all of the catalyst used in the preparation. While there are several Varieties of products answering this description, they are all more or less alike and the generic class will be referred to as technical tolyl dichlor phosphine in the discussion following as well as in the attached claims. When the preparation of tolyl dichlor phosphinc is carried out according to the directions given in the literature (Liebigs Annalen vol. 212, p. 206-7) the product after the reaction, separates into two layers. The upper layer consist essentially of unreacted hydrocarbon and phosphorus trihali'de together with a small amount of tolyl dichlor phosph-ine. The bottom layer contains'most of the tolyl dichlor phosphine together with small amounts of unreacted material and most of the catalyst. the latter most probably being in the form of a complex addition product. The crude mixture remaining after drawing off the upper layer, i. e. the bottom layer, can be reacted directly with the rubber reclaim or scrap and is in fact preferred to pure tolyl dichlor phosphine.

While the above picture applies when the proportion of catalyst reported in the literature is used, it has been foundthat the reaction can be driven further toward completion by increasing the proportion of catalyst so that eventually no layers separate. However, the product produced, at least for the purposes of this invention, is equivalent to that described above and in fact appears to be identical in every respect. -In addition the crude reaction product, whether a bottom layer or an entire reaction mixture obtained with a higher proportion of catalyst, may be heated up to distill out unreacted phosphorus trichloride and toluene or alternatively sufiicient catalyst used to consume substantially all of the reactants. Obviously the resulting product is not a weight for weight equivalent of the '20 product just mentioned since it contains a higher proportion of active constituent. It will, therefore, be-hereinafter referred to as stripped tolyl dichlor phosphine and the unstripped varieties will be called crude tolyl dichlor phosphine.

26 Accordingly technical tolyl dichlor phosphine may be either the crude or fstripped variety. The following example illustrates in detail the preparation of technical tolyl dichlor phosphine:

Into a suitable glass or glass lined reaction ves- 30 sel fitted with a reflux condenser there was temperature it was maintained for about 36 hours. When cool the reaction mixture separated into two portions. The bottom layer amounting to substantially 840 parts by weight was drawn ofi and either immediately reacted with rubber or stored in moisture proof containers. These precautions ar'eadvisable because tolyl dichlor phosphine' and analogous materials by drolize to the corresponding acids. However,- the presence of small amounts of Water during the subsequent reaction with the rubber has no noticeable effect.

When the aluminum chloride was increased to 140 parts by weight in the foregoing procedure, no layers separated. The entire reaction charge 50 of crude tolyl dichlor phosphine is a weight for phos 55 gave approximately 500 parts by weight of stripped tolyl dichlor phosphine. Obviously, the total quantity of unreacted material separated from a given reaction will be known and it is a simple matter to calculate the quantity of stripped product equivalent to a given weight of the crude.

There isno advantage in using chemically pure retene since a technical grade formed in the distillation of pine tar oil resulting from the destructive distillation of pine wood or rosin can be used. The usual process comprises vacuum distilling the ordinary pine tar oil of commerce to obtain the light, medium and heavy pine tar fractions. Then, by a further distillation of the residue under pressure, the wood phenols and neutral retene oil are obtained. This neutral retene oil contains up to about 35% retene, the remainder being for the most part, .hydroretene. Either the neutral retene oil or a technical grade of retene obtained therefrom can be used in the practice of the present invention and are substantially equivalent. Technical retene and neutral retene oil are terms having a well defined meaning and are so used in the present specification. In general any crude commercial retene containing as the impurity other hydrocarbon products from the distillation of wood can be used.

As indicated above, the scrap or reclaimed rubber, tolyl dichlor phosphine and crude retene must be combined within a certain critical range of proportions in order to achieve the combination of properties desired. In particular, it has been found that any reclaimed or scrap rubber is enormously improved with regard to resistance to solvents and ozone providing that the rubber is treated with technical dichlor phosphine equivalent to at least 60 parts by weight of the crude and at least 40 parts by weight of technical retene or retene oil per 100 parts by weight of the rubber. For best results the proportion of each reactant should be from '70 to 85 parts by weight, the optimum being about 80. Since excessive amounts of either the phosphine halide or retene decrease the rubbery properties the upper limit is equally important. The technical tolyl dichlor phosphine should always be used in a proportion equivalent to less than 3.00 parts by weight of crude" and the technical retene should likewise be less than 100 parts by weight per 100 parts by weight of rubber. Furthermore, while it is to be emphasized that any variations within the limits specified are permitted, it is preferred to treat the rubber with equal weights of crude tolyl dichlor phosphine and retene or at least to use as much retene as crude tolyl dichlor phosphine and preferably from '70 to 85 parts of each ingredient. are not only solvent and ozone resistant but possess a maximum of rubbery properties. After compounding and curing in a stock carrying 40 parts of carbon black the hardness is below 90 as measured by a Shore durometer type A and there is negligible if any cracking after three minutes exposure of the stock to ozone of such concentration that a similar stock compounded from smoked sheets of rubber is badly cracked after an exposure of one minute.

In order to produce the new plastic products it is essential that the reactants be brought into intimate and uniform association. To this end use of a solvent as for example benzene, toluene or carbon disulfide is of considerable benefit. However, an efficient internal type mixer of corrosion resistant material such as stainless steel will give the proper association of reactants in which case the solvent can be eliminated.

The temperature range preferred for carrying out the reaction ranges from the boiling point of a carbon bisulfide cement to about 60 C. While either higher or lower temperatures can be used, there is no advantage sincebelow room temperature the reaction is unduly prolonged and at higher temperatures the reaction and in turn, the properties of the final products, are more diflicult to control although the reaction will of course be complete in a shorter time. However, from about room temperature up to about 60 C. the time of reaction is not especially critical. Comparable results are obtained by initially associating the rubber and tolyl dichlor phosphine in toluene, carbon bisulfide or similar solvent for from one to three hours, adding the retene and continuing the reaction for from 6 to 24 hours.

The following specific examples will illustrate the preparation in detail and are to be understood as descriptive and explanatory but not limitative of the invention.

Example I Substantially 100 parts by weight of ground truck peels were dispersed in a suitable solvent as for example toluene andsubstantially 80 parts by weight of crude tolyl dichlor phosphine added thereto. The charge was stirred and heated at about 55 C. for about two hours and substantially 80 parts by weight of technical retene added.

Heating and stirring at 55 C. was continued for about 18 hours after which the solvent was removed, preferably by distillation. Heating was continued for a short time after distillation had The products then i substantially ceased and then live steam was introduced. After a thorough steaming out the charge was removed and washed with Water on a rubber mill, preferably one having corrugated rolls, or on other equipment especially adapted for washing tough plastic products. The product was dried by milling on a hot mill followed by heating to constant weight in a vacuum oven. Substantially 202 parts by weight of tough rubbery product resistant to ozone and solvents was obtained.

Example II Into an internal type mixer of suitable capacitv there was charged substantially 200 parts by weight of ground truck peels and substantially 160 parts by Weight of technical retene. The charge was rendered homogenous by blending for about two hours and then substantially 160 parts of crudetolyl dichlor phosphine added and the mixer run for another two hour period. Heat was then applied suflicient to raise the temperature to 60 C. and the charge heated for about 3 hours. Water or dilute alkali was then added and the product washed until neutral. The final Washing is most conveniently carried out on a rubber washing mill. After drying to constant weight 414 parts by weight of tough rubber like plastic was obtained.

Example III Substantially 200 parts by weight of ground truck peels were charged into an internal type mixer of suitable capacity and masticated at about C. to drive out any entrained water. While not essential, this step is desirable in order to effect a closer control over the properties of the final product and can be advantageously applied to a mixture of the rubber and retene ingredient as well as to either or both of them sep- Hardnesswas measured on a Shore durometer arately. substantially 160 parts by weight of type A. The immersion'tests are self-explains. neutral retene 011 was then added and after tory. f a I 1 I Percent change in Tecli.tolyl Tech. Hsrda I -v wt. after 72 his. dichlor retene,. .ness Crack ng after 3, mm. immersion at Stock No. phosphine, 'parts alter ex osure to ozone room temp. in

parts by by 'cure under stress weight weight vShore l 688011116 Lubeoil 1.... :50crude.. 50 Craokedbadly +212 --2.1 a a a: 3'8 3 7' s2 70 77 2;5 ---2.6 so 70 7s +0.2 .-2.5 30. 70 1o 3.2 I -ao 70 88 +2.3 -LO a ii at 5a ..50stripe 5b p so '78 +4.4 4.1 80 so .do.. +7.3 5.1 5 .9 t I L. 100 1 76 (Low tensile strength; lazy cur-cs2. 8 80stripped.. Z0 {95 Visible cra'c lng... 9 ,d0 40 I ;-N0'D0. 10.; so 91 ..do.

1 R. oil.

blending about an hour to assure homogeneity, substantially 160 parts by weight of crude tolyl dichlor phosphine added and the blending continued for another hour. In this connection, it is possible that an appreciable reaction has taken place at this stage. The temperature was raised to 60 for about 4 hours and the reaction terminated by the addition of water. The product was washed with water or better with dilute alkali and finally with water, until neutral and dried to constant weight. substantially 412 parts by weight of tough rubber like plastic was obtained.

As illustrative of the useful properties of the new products stocks were com-pounded comprising plastic 100, zinc oxide 10, carbon black 40, sulfur 5, mercaptobenzothiazole1.5, stearic acid 3, pine tar 2 and acetone-p-amino diphenyl condensation product 1.5 (all parts are by weight). The stocks were cured by heating in a'press in the usual manner and examinations made into the physical properties of the cured rubber products. The table set forth below summarizes the results and shows the proportion of reactants used in making the products in relation to the results obtained. All proportions are based on 100 parts by weight of the scrap or reclaimed rubber. The 50 parts ofstripped tolyl dichlor phosphine used to make the product from which stock No. 50. was compounded was obtained from 80 parts of the crude. '80 parts of stripped (stocks 8-10) corresponds to about 128 parts of crude. The plastic rubber derivative used in stocks Nos. 1 3a, 6 and 7 was made from Midw'est whole tirer reclaim following Example I above; that used in stock 3b was made from Xylos ground scrap following ExampleI; that in stock 30 was made from Midwest ground black inner tubes following Example I and that used in stocks Nos. 2, 3, 4, 5, 5a, 8 and 10 was made from ground truck peels 'foll'owing Example I. The product of Example II was used in stock 522 and the product of Example III was The above data show that at least 40. parts by weight of technical reteneor retene oil are necessary to impartresistance toozone, gasoline, lubricating oil and the like and that this is so inspite of the fact that the'proportion'of tolyl dichlorphosphine may be excessive. (stocks 8, 9 and l0). Itis further evident that a proportion oftolyl dichlor phosphine equivalent 130;60'

parts by weight of the crude" is necessary for good resistance to ozoneistocks 1 and 2). On the other hand,.,as much as .100 parts-of. the-phosphine' halide--- renders the product hardand brittle istockfi). Whilethis can be overcome byincreasing the retene ingredient to parts,

this sacriflces'the physical properties, particu-- larlythe tensile strength of the resulting products. l This invention-is not limited-to thespecifie examples and compositions set forth to illustrate the invention.- Other solvents as for example carbon. disulfide, benzene, xylene and the like may be used or wherefollowing Example II or III asmall proportion of a solvent may be added to aid the blending. Other fillers, compounding, and vulcanizing ingredients than those particularly mentioned maybe utilized. Furthermore, the new'plastic products of this invention can be admixed with. other-gums or resins whether oi. natural or synthetic origin. This invention is limited solely by the claims attached hereto as part of the present specification.

What'is claimedis: w I. The method of making anew plastic product which comprises intimately mixing a member of a group consisting of-scrap rubber and reclaimed rubber with technical tolyl dichlor phos'phine having one tolyl radicle and two chlorine atoms directly attached to a trivalentphosphorus atom and consisting of'thereaction product containing the catalyst complex of toluene and P013 inthe presence of aluminum chloride catalyst and ret'ene in the proportion of substantially 100 parts by weightwof the rubber, technical tolyl dichlor phosphine equivalent to at least 60' but less than 100 parts by weight of crude tolyl dich'lor phosphineand at least 40 but less than 100' parts by weight of said retene ingredient and heating the mixture. I

2; The method of making a new'pl'astic product which comprises intimately mixing remember of a group consisting of scraprubber and reclaimed rubber with technical' tolyl-dichlor phosphine having one tolyl radicle and two chlorine atoms directly attached to a trivalent phosphorus atom and consisting of the reaction product containing the'catalyst complex of toluene and P013 in the presence of aluminum chloride catalyst and a crude cheap grade of retene in the proportion of substantially 100 parts by weight of the rubber, technical tolyl dichlor phosphine equivalent to at least 60 but less than 100 parts by weight o1 crude tolyl dichlor phosphine and at least 60 but less than 100 parts by weight of said retene ingredient and heating the mixture. f

3. The method of making anew plastic product which comprises intimately mixing a member of a. group consisting of scrap rubber and reclaimed rubber with technical tolyl dichlor phosphine having one tolyl radicle and two chlorine atoms directly attached to a trivalent phosphorus atom.

and consisting of the reaction product containing the catalyst complex of toluene and PC13 in the presence of aluminum chloride catalyst and technical retene in the proportion of substantially 100 parts by weight of the rubber, technical *toIyldichIor phosphine equivalent to from '70fto 85 parts by'weight of crude tolyldichlor phosphine and from 70' to 85 parts by weight'of saidretene 'ingredient and heating the mixture.

4. The method of making a new plastic product which' comprises intimately mixing a member of a group consistingof is'crap rubber and reclaimed rubber withtechnical' toylyl dichlor phosphine having" one tolyl radicle and two chlorine atoms directly attached to a trivalent phosphorus atom and"consisting of the reaction product containing' the catalyst complex of toluene and PCls'in the'pre'senc of aluminumchloride catalyst and neutral retene oilin' the proportion of substantially 100 parts by weight of therubber, technical tolyl dichlor'pho'sphine equivalent to 80 parts by weight of crudetolyl dichlorphosphine and '80 parts by weight of 'saidfretene' ingredient and heatingthemixture' v The methodof making a new plastic product which comprises intimately mixing a member of 'agroup consisting of scrap rubber and reclaimed rubber with technical tolyl dichlor phosphine having one tolyl radicle and two chlorine atoms directly attached to a trivalent phosphorus atom and consisting of the reaction product containing the catalyst complex of toluene and PCla' in the presence of aluminum chloride catalyst and neutral retene'oil in the proportion of substantially 100 parts by weight of the rubber, technical tolyl dichlor phosphine equivalent to from '70 to 85 parts by weight of crude tolyldichlor phosphine and from '70 to 85 parts by weight of neutral retene'oil and heating the mixture. i

6. The method of making a' new plastic product which comprises 'intimatelymixing a member of a group consisting of scrap rubber and'reclaimed rubber in an' organic-solvent below' 60" C. with technical dichlor phosphine having one tolyl radicle and two chlorine atoms directly attached to a trivalent phosphorus atom and consisting of the reaction product containing the catalyst complex of toluene and PCls in the presence'of aluminum chloride catalyst equivalent to at least 60 but less than 100 parts by weight of crude tolyl dichlor phosphine per 100 parts by weight ofthe rubber andlfurther reacting the product under the same conditions with at least 60 but less than 100 parts byweight of a crude'cheap gradevof retenep. t,

7. The method of making a new plastic product which comprises intimatelymixing 100 parts by weight of a member of a group consisting of scrap rubber and reclaimed rubber with from '70 to 85 parts by weight of crude tolyl dichlor phosphine comprising the structure in an organic solvent for from 1 to 3 hours above room temperature but below 60 C. to effect a partial reaction and further treating the product with from 70 to 85 parts by weight of technical retene by heating for from 6 to 24 hours under similar conditions.

8. The method of making a new plastic product which comprises masticating substantially 100 parts by weight of a member of a group consistingof scrap rubber and reclaimed rubber with from '70 to 85 parts by weight of technical retene,

adding tolyl dichlor phosphine comprising the structure equivalent to from -85 parts of crude tolyl dichlor phosphine and efiecting a reaction by mild heating.

9. The method of making a new plastic product which comprisesintimately mixing 100 parts by weight of ground truck peelsrubber with parts by' weight of crude tolyl dichlor phosphine comprising the structure I OH: P\

in toluene 'at'55 C. for 1 to 3 hours to efiect a partial reaction and further treating with 80 parts by weightof technical retene for about 18 hours at 55 C.

10. An elastic rubber like sulfur vulcanizable derivative of a member of a group consisting of scrap rubber and reclaimed rubber which has high resistance to cracking in ozone, very low absorptive capacity inlubricating oil and gasoline obtained by intimately mixing 100 parts by weight of the rubber with technical tolyl dichlor phosphine having one tolyl radicle and two chlorine at'om's directly attached to a trivalent phosphorus atom and consisting of the reaction product containing the catalyst complex of toluene and P013 in the' presence of aluminum chloride catalyst equivalent to at least 60 "but less than 100 parts by weight of crude tolyl dichlor phosphine and'at least 40 but less than 100 parts by weight of retene and heating the mixture.

11. An elastic rubber like sulfur vulc'anizable "derivative of a member of a group consisting of scrap rubber and reclaimed rubber which has high resistance to cracking in ozone; very low absorptive' capacity in lubricating oil and gasoline obtained by intimately mixing 100 parts by weight of therubber with technical tolyl dichlor rine atoms directly attached to a trivalent phosphorus atom and Consistingof the reaction'product .containing'the catalyst complex of toluene and PC13 in'the'presence of aluminum chloride catalyst equivalent to from '70 to parts by weight of crude tolyldichlor phosphine and from :70 to 85 parts by weight of neutral retene oil and heating the mixture.

12. An elastic rubber like sulfur vulcanizable derivative of a member of a group consisting of scrap rubber and reclaimed rubber which has high resistance to cracking in ozone, very low absorptive capacity in lubricating oil and gasoline obtained by intimately mixing 100 parts by weight of the rubber with technical tolyl dichlor phosphine having one tolyl radicle and two chlorine atoms directly attached to a trivalent phosphorus atom and consisting of the reaction product containing the catalyst complex of toluene and PCI; in the presence of aluminum chloride catalyst equivalent to from '70 to 85 parts by weight of crude tolyl dichlor phosphine and from 70 to 85 parts by weight of technical retene and heating the mixture.

13. An elastic rubber like sulfur vulcanizable derivative of vulcanized ground scrap rubber which has high resistance to cracking in ozone, very low absorptive capacity in lubricating oil and gasoline obtained by intimately mixing 100 parts by weight of the rubber with technical tolyl dichlor phosphine having one tolyl radicle and two chlorine atoms directly attached to a trivalent phosphorus atom and consisting of the reaction product; containing the catalyst complex of toluene and P013 in the presence of aluminum chloride catalyst equivalent to from 70 to 85 parts by weight of crude tolyl dichlor phosphine and from '70 to 85 parts by weight of neutral retene oil and heating the mixture.

14. An elastic rubber like sulfur vulcanizable derivative of vulcanized ground scrap rubber which has high resistance to cracking in ozone, very low absorptive capacity in lubricating oil and gasoline obtained by intimately mixing 100 parts by weight of the rubber with technical tolyl dichlor phosphine having one tolyl radicle and two chlorine atoms directly attached to a trivalent phosphorus atom and consisting of the reaction product containing the catalyst complex of toluene and PCI: in the presence of aluminum chloride catalyst. equivalent to from 70 to 85 parts by weight of crude tolyl dichlor phosphine and from '70 to 85 parts by weight of technical retene and heating the mixture.

15. An elastic rubber like sulfur vulcanizable derivative of a member of a group consisting of scrap rubber and reclaimed rubber which has high resistance to cracking in ozone, very low absorptive capacity in lubricating oil and gasoline obtained by intimately mixing 100 parts by weight of the rubber with approximately 80 parts by weight of crude tolyl dichlor phosphine comprising the structure 01 CHaOP and approximately 80 parts by weight of a crude cheap grade of retene and heating the mixture. 16. An elastic rubber like sulfur vulcanizable derivative of vulcanized scrap rubber which has high resistance to cracking in ozone, very low absorptive capacity in lubricating oil and gasoline and in which the vulcanized scrap rubber makes up only about half the total product obtained by intimately mixing 100 parts by weight of vulcanized scrap rubber with approximately 80 parts by weight of crude tolyl phosphine dichloride comprising the structure CHQOP and approximately 80 parts by weight of technical retene and heating the mixture below C.

17. An elastic rubber like sulfur vulcanizable derivative of ground truck peels rubber which has high resistance to cracking in ozone, very low absorptive capacity in lubricating oil and gasoline and in which the ground truck peels make up only about half the total product obtained by intimately mixing 100 parts by weight of ground truck peels with approximately parts by weight of crude tolyl phosphine dichloride comprising the structure 01 CHi-P and approximately 80 parts by weight of technical retene and heating the mixture below 60 C.

DAVID J. BEAVER. 

